New NOAA supercomputer boasts a Linux architecture

The Linux open-source operating system powers a new government supercomputer that will help meteorologists forecast the weather more accurately.

Using the Rapid Update Cycle weather model, NOAA's Jet supercomputer produced this 36-hour forecast for the contiguous United States. Colors indicate temperatures and arrows indicate winds.

The $17 million, 273-processor supercomputer, dubbed Jet, went live in late February and made its public debut April 26 at the National Oceanic and Atmospheric Administration's Forecast Systems Laboratory in Boulder, Colo.

When all of its 1,536 planned processors arrive in early 2002, Jet will join the elite ranks of systems capable of performing trillions of calculations per second.

What makes Jet different from most other top supercomputers is its Linux architecture, which helped a small systems integrator beat large server makers in winning the contract.

'This was one of the first competitive procurements won by a Linux supercomputer,' said Luke Lonergan, technical director of High Performance Technologies Inc. of Reston, Va., which built the system for NOAA.

High Performance Technologies and other bidders had to benchmark seven weather models at top speed on their prototype machines, Lonergan said.

Other government researchers have built parallel Linux supercomputers from commodity parts, such as the CPlant and Avalon clusters at Energy Department laboratories. Such machines, generically called Beowulf clusters, are often considered experimental.

Jet is the first Linux cluster in a 'real production research environment,' High Performance Technologies president Don Fitzpatrick said.

The technology is advancing so rapidly that such a Linux system would not have been feasible even a year ago, said A.E. 'Sandy' MacDonald, director of the forecasting lab.

A previous version of Compaq's Alpha processor would have yielded the same peak-speed benchmark but much less sustained speed on real-world problems, Lonergan said.

The sustained speed of the Alpha EV6.7 is about 30 percent of its peak and roughly twice as high in sustained performance as its predecessor.

Later this year, an interim upgrade will give Jet a total of 512 processors with a potential peak of about 900 GFLOPS.

By early 2002, NOAA will add another 1,024 processors to Jet, Lonergan said. The total of 1,536 processors will give it a theoretical peak of 2 trillion to 4 trillion floating-point operations per second.

Linking the processors is a Myrinet scalable interconnect system from Myricom Inc. of Arcadia, Calif.

Company engineers modified the Linux kernel to run the drivers. They also made changes to the Myrinet software and to the Portable Batch System, an open-source batch queuing system developed at NASA Ames Research Center in Moffett Field, Calif.

The company has provided an open-source version of its code modifications, Lonergan said.

More to come

The initial Jet installation doesn't even use Linux symmetric multiprocessing capabilities, because the systems management software and the Myrinet interconnect together make the 256 processors act like one, Lonergan said. Later upgrades of Jet, however, will take advantage of SMP to boost performance.

Jet has a 750G storage area network plus a robotic tape drive from Advanced Digital Information Corp. of Redmond, Wash., that can hold 72T of data, Lonergan said.

Forecasting lab researchers will use Jet primarily to refine simulations for the National Weather Service and other agencies. They want to improve the accuracy of the Rapid Update Cycle model for predicting nationwide weather over short time scales.

The lab is working with NOAA's National Centers for Environmental Prediction and the University of Oklahoma to develop next-generation weather models that forecast precipitation more accurately than today's simulations, MacDonald said.

Current weather models are limited to resolutions of roughly 50 miles. Storms much smaller than 50 miles across, such as thunderstorms, slip through the cracks. Researchers want to predict more localized weather features that are only one or two miles across, and the continuous advances in computing are helping meteorologists get closer to that goal, MacDonald said.

Public expectations for timely and accurate forecasts have grown over the last two decades. The improved models should make a noticeable difference in forecast precision over the next few years, he said.